Sustainable resin development for the strategic upcycling of waste fly ash into high-performance polymer composites

Surface-coated fly ash used as filler in biodegradable poly(vinyl alcohol) composite films: Part 1—The modification process

Fly ash was modified by being mixed with silane coupling agent for 10min, 20min, 30min, 40min and 50min. Pure ABS, compounded materials consisting of unmodified and modified fly ash and ABS were extruded into filaments. 3D printed specimens were manufactured with extruded filaments. Results show, ABS filaments have good 3D printing process and product performance and unmodified fly ash is harmful to ABS filaments. To improve interface bonding between ABS and fly ash, silane coupling agent can be introduced, and mixing it with fly ash for 30min may be a better choice, which has better dimension stability, impact strength and tensile strength.

Composite films of poly(vinyl alcohol) (PVA) and chemically modified fly ash (MFA) by sodium hydroxide were prepared by aqueous cast method with 5, 10, 15, 20 and 25 wt% MFA treated with 1 wt% cross-linking agent (glutaraldehyde, GLA). The tensile strengths of the composite films were found to increase proportionally with MFA and the maximum strength attained was 414% higher in the case of 20 wt% MFA than that in neat PVA film. The percentage of strain at break exponentially decreased with addition of MFA. The modulus of the composites was determined to increase proportionally up to a maximum 685% at 20 wt% MFA compared to that of neat PVA film. Interfacial networking between the MFA and PVA was evident from scanning electron microscopy (SEM) images of tensile-fractured surfaces, which was not observed for the unmodified fly ash (FA) system. Atomic force microscopy (AFM) analysis showed that the mean square surface roughness of the composite films of PVA–MFA was 53% smoother than the films with FA.

Fly ash as residue from coal combustion has potential for environmental applications as an adsorbent for water pollution treatment. Adsorption performance of fly ash depends on fly ash origin and chemical treatment. Modification by the chemical treatment could increase the adsorption capacity. In this paper, fly ash was alkali modified with NaOH solution at various concentrations (2 N, 4 N, 6 N, 10 N) at a temperature of 60 °C. The physical properties and structural characteristics of unmodified fly ash and alkali modified fly ash were studied from Brunauer-Emmett-Teller (BET) surface area and pore size analysis, and also scanning electron microscope (SEM) analysis. The results showed that alkali modification could increase surface area, average pore radius, and total pore volume in fly ash. Unmodified fly ash and alkali modified fly ash could be classified as mesoporous materials and exhibited type IV nitrogen adsorption-desorption isotherms with H3 hysteresis loop according to the classification of the International Union of Pure and Applied Chemistry (IUPAC). SEM observations revealed that modified fly ash had rougher surface and more porous structure than that of unmodified fly ash. Alkali modification had changed the physical properties and structural characteristics of fly ash that supports its application as an adsorbent.

Fly ash reinforced polyetheretherketone (PEEK) composites were fabricated using compression molding technique. The fly ash surface was chemically modified using vinyltrimethoxy silane and 3‐aminopropyltriethoxy silane. The properties of treated fly ash PEEK composites were examined in terms of scanning electron microscopy, dynamic mechanical thermal analysis, differential scanning calorimetry, and thermo gravimetric analysis. The modified fly ash was observed to disperse more uniformly than the unmodified counterpart. The tensile strength and modulus also improved with treated fly ash filled PEEK composites. The increment of the dynamic modulus for the PEEK/treated fly ash composites is 32% at 250°C, indicating apparent improvement of high temperature mechanical properties. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers.

In this research, fly ash was modified with acids, such as HCl, H2SO4 and mixture of both and alkali with hydrothermal method. XRF analysis showed a decrease of CaO and Fe2O3 contents in HMFA, SMFA and HSMFA while AMFAWH has higher CaO content and produced the new zeolite phase (hydroxy-sodalite) in 2 θ = 24.232 ° from XRD test. FTIR analysis showed that the fly ash gave absorption band of O-H group, H-O-H bend group, and Si-O stretching group. SEM images showed that acid-modified fly ash indicated a deposition of gehlenite crystals while AMFAWH showed flat rectangular shaped small particle known as hydroxy-sodalite. The BET method analysis indicated that all adsorbents were classified as mesopores. The experimental data showed that adsorption efficiency and capacity of fly ash was improved significantly after modification. The unmodified fly ash (UFA) has the highest phosphate adsorption efficiency and capacity in 0.16 g was 60.07 % and 0.485 mg P-PO4/g while modified fly ash (HSMFA) was 85.62 % and 0.705 mg P-PO4/g. The optimum contact time were obtained at 240 min for UFA, HMFA, SMFA and 480 min for HSMFA and AMFAWH. The optimum of pH were obtained at pH 5 and pH 7 for the others. The fifth adsorbents follow the Freundlich isotherm and pseudo-second-order kinetic model in phosphate adsorption.

Mine effluents represent a serious environmental problem on a global scale. Therefore, the effective treatment of this water is a serious issue in the scientific field. The adsorption process seems to be one of the attractive methods, especially due to the simplicity of design, affordability or high efficiency. The latest scientific knowledge has shown that the use of waste and natural adsorbents is economical and effective. This study aimed to evaluate the efficiency of the adsorption process of natural and waste materials—zeolite, bentonite and fly ash—under the influence of temperature and modification of these adsorbents. The novelty of this study resides in an adjustment of the modification method of adsorbents compared to previous research: thermal–alkaline treatment versus hydrothermal one. Another novelty is the use of modified fly ash from biomass combustion as an adsorbent in comparison with the previously used fly ash from coal combustion. The modification of the adsorbents made the adsorption process more effective at all experimental concentrations. The characterisation of adsorbent samples was performed using X-ray diffraction (XRD). The parameters of the adsorption isotherms, Langmuir, Freundlich and Temkin, were estimated by nonlinear regression analysis. The adsorption capacity of Cu(II) of fly ash was comparable to natural adsorbents. Adsorption processes were better described by pseudo-second-order kinetics. At the end of this study, the suitability of using the adsorbents to reduce the concentration of Cu(II) in neutral mine effluents was observed in the following order at 30 °C: unmodified fly ash > modified bentonite > unmodified zeolite. At the temperatures of 20 °C and 10 °C, the same trend of the suitability of adsorbents use was confirmed: modified bentonite > modified zeolite > modified fly ash. The practical applicability of this study lies in the expansion of knowledge in the field of adsorption processes and in the improvement of waste management efficiency of heating plants not only in Slovakia, but also globally.

Preparation and characterization of thermoplastic starch composites with fly ash modified by planetary ball milling

This paper presents the characteristics of fly ash which was modified by 2-mercaptobenzothiazole (MBT) and sodium dodecyl sulfate (SDS) as the surfactants after treating with 1M NaOH solution. The change in morphology, specific surface area, crystal structure, and composition of the unmodified and modified fly ash was evaluated by FTIR, XRD, FESEM, BET, and EDX methods and techniques. The FTIR spectra of modified fly ash showed that there was no chemical reaction between the surfactants and fly ash. The XRD patterns and FESEM images indicated that modified fly ash had zeolite structure with a pore size of about 50 nm. Heavy metal ion adsorption behavior as well as adsorption isotherm models (Langmuir and Freundlich) of Cd2+ and Hg2+ ions of the unmodified and modified fly ash were also investigated and discussed. The amount of adsorbed ions of the modified fly ash was higher than that of the unmodified fly ash. The calculated results from the adsorption data according to the adsorption isotherm models of the above ions displayed that the Langmuir isotherm model was complied for the Cd2+ adsorption process while the Freundlich isotherm model was fitted for the Hg2+ adsorption process.

Fly ash (FA) is promising for environmental remediation, but how to modify the FA with high remediation efficiency through an environmentally friendly and low-cost modification method is scare. A modified FA (MFA) was prepared through a one-step hydrothermal modification with Ca(OH)2 and KH2PO4. Results indicated that irregular agglomerates occurred on the surface of the MFA and that the specific surface area increased by 1.94 times compared to that of FA. Compared to FA, glassy compositions in MFA were destroyed and amorphous Si/Al and alkaline aluminosilicate gels were formed. The soil application of 0.2–0.6% MFA significantly increased soil pH by 0.23–0.86 units compared to FA and decreased available lead (Pb) and copper (Cu) by 25–97.1% and 13.5–75%, respectively. MFA significantly decreased exchangeable Pb and Cu by 12.5–32% and 11.4–35.2%, respectively, compared to FA. This may be due to the high pH and specific surface area of MFA, which promoted to the formation of amorphous Si/Al, metal–phosphate precipitation, and complexation with functional groups. In addition, MFA slightly increased the biomass of shoots and roots and decreased the uptake of Pb and Cu by ryegrass. This study provides a new modification method for the utilization of FA in the heavy metal-contaminated soils.

A silica-rich material was generated from waste fly ash and it was subsequently characterized and experimented in ESBR compounds to find its suitability to be used as a filler for rubber compounds. This material contained 97.5% silica and 2.5% alumina. Characterisation of this material, designated as Modified Fly Ash (MFA), revealed the presence of characteristic peaks of silica in an FTIR study, and the surface area was found to be 110–115 m2/g. The effect of this material as a filler for rubber compound has been studied in ESBR compounds at low, medium and high filler loadings, and the compound properties were compared with those of compounds filled with two commercially available grades of silica, namely VN2-Silica (surface area 120–125 m2/g) and VN3-Silica (165–170 m2/g), at similar loadings. MFA showed the highest cure rate index, elongation at break and lowest heat generation among the three fillers at all the levels of filler loading. The tensile strength and 300% modulus of MFA filled compounds were inferior to those of VN3-silica, but they were closer to the values obtained for VN2-silica filled compounds. These two properties of MFA and VN2-Silica were comparable at low filler loading and at medium to high loading, the properties exhibited by VN2-Silica could be matched by using higher dosage of MFA.

Study on the phosphate removal from aqueous solution using modified fly ash

Pozzolanicity of fly ash modified by fluidized bed reactor–vapor deposition

This study focused on the characteristics of the removal of Cr(VI)(Cr6+) from wastewater with fly ashes(FAs), a by-product from coal-fired electric power plants. The influences of NaCl dose, pH, agitated time and fly ash(FA) dose(the temperature is 50℃in the test) were investigated in batch experiments, and the removal of Cr6+ and sorption capacity with modified fly ashes(MFAs) were compared to those with original fly ashes(OFAs). With the initial Cr6+ concentration 2mg/L at pH=2, the removal of Cr6+ was 98.7% in 60min with 2g/L MFAs by 0.25M H2SO4 solution. The equilibrium process was described well by the Langmuir isotherm model with maximum sorption capacities of Cr6+ on MFAs. Good correlation coefficient was obtained for the pseudo second-order kinetic model. In the end, some mine wastewater containing low concentration of Cr6+ was treated by MFAs. It could be proposed that MFAs by 0.25M H2SO4 is an effective adsorbent for the removal of Cr6+ from wastewater. Meanwhile, Our objective is to search a kind of low-cost adsorbent as a replacement for costly conventional methods of removing heavy metal ions(Cr6+) from wastewater with FAs, to improve the utilization ratio of FAs and to pursue a new approach for environmental protection and recycle treatment of a coal combustion by-product. Study on the associative methods for MFAs and advanced treatment which should be strengthened will offer the theoretical foundation for the practical application, and finally, this will realize zero emission of Cr6+.

The performance and application of fly ash modified by PDMDAAC